Abstract: The present invention is directed to a signal amplifier apparatus adapted for carrying out delta-sigma modulation of an input signal to carry out pulse width modulation of that signal S1 to obtain PWM signal S2 to amplify this PWM signal S2 by an amplifier so that a signal S3 of a predetermined magnitude is provided, wherein the signal amplifier apparatus comprises a correction circuit (104) for correcting output of a quantizer (103) provided at a delta-sigma modulation device (10), and the correction circuit (104) is installed (provided) at feedback path with respect to the input side from the quantizer (103) or immediately before a pulse width modulator (11) to thereby correct distortion taking place at the amplifier.

Abstract: A digital power amplifier including a switching control device for generating a first switching control signal and a second switching control signal which results from inverting the first switching control signal at an equal timing based upon an inputted audio signal, wherein the first and second switching control signals generated from the switching control device are respectively supplied to control terminals of first and second switching devices so that the first and second switching devices are driven in a push-pull manner to produce an audio signal amplified when the power source is switched. Output characteristics are prevented from being deteriorated by noise from the power source by canceling out radiation of the signals generated from the two switching devices and deterioration of outputted audio characteristics due to noise from the power source is prevented.

Abstract: A power amplifier circuit includes a pair of PWM circuits, to which an input signal is supplied, a pair of push-pull circuits, and drive circuits for supplying the outputs of the PWM circuits to the push-pull circuits as drive signals. A speaker is arranged between the output end of one push-pull circuit and the output end of the other push-pull circuit. The drive circuits alternately drive the respective push-pull circuits every cycle time of a PWM signal. The circuit can suppress radiation caused by the variation in output voltages.

Abstract: A sampling frequency conversion apparatus which easily controls the phase difference (time difference) between the input data and the output data in converting the sampling frequency, and comprises storage means 13 for continuously writing the input data or the data obtained by over-sampling the input data and for continuously reading out the data written maintaining a predetermined address difference relative to the write address, and interpolation processing means 14 for interpolating the data read out from the storage means 13 to obtain data of which the sampling frequency is converted. In converting the sampling frequency, an address difference between a write address and a read address in the storage means 13 is optimized, the address difference being optimized without limitation for a predetermined period of time from the start of supplying the input data and, then, being optimized by imposing a predetermined limitation after the passage of the predetermined period of time.

Abstract: A digital power amplifier includes a switching control means for generating a first switching control signal and a second switching control signal which results from inverting the first switching control signal at an equal timing based upon an inputted audio signal, wherein the first and second switching control signals generated from the switching control means are respectively supplied to control terminals of first and second switching means so that the first and second switching means are driven in a push-pull fashion to thereby produce an audio signal amplified when the power source is switched. Thus, it is possible to prevent output characteristics from being deteriorated by noise from the power source by canceling radiation of the signals generated from the two switching means each other out. Therefore, in the digital power amplifier, outputted audio characteristics can be prevented from being deteriorated due to the influences exerted by noise from the power source.